It is known that porous bodies for chromatographic use having both through-flow channels and a skeleton (referred to as “monoliths”) have advantages which cannot be obtained by conventional particle-packed columns. For example, when such a porous body is used as a separation medium for HPLC, high column performance can be achieved due to its wide flow channels and thin skeleton and performance degradation can be reduced even at a high flow rate due to its low pressure loss. High-performance monoliths mainly made of silica gel have already been realized by microstructure control, and some of them are commercially available.
On the other hand, organic polymer monoliths are also known. Conventional organic polymer monoliths are formed by combinations of hydrophobic monomer components and poor solvents as pore-forming solvents (porogens). In a solution system containing a hydrophobic monomer component and a poor solvent, Van der Waals force between growing polymer chains becomes stronger than the steric hindrance of the polymer chains, and therefore the polymer chains aggregate. This causes nuclear formation due to the entanglement of the polymer chains, growth of microgel particles due to the aggregation of the polymer chains, and a rapid increase in the surface energy of the system. Further, the microgel particles aggregate and become coarse by similar growth (fractal growth) so that a gel is formed. In the case of such a solution system, gel formation is due to particle aggregation, and phase separation competes with gelation and occurs at a very early stage so that a monolithic structure with a small specific surface area is fixed. In this case, a particle-aggregation-type monolith is formed. Therefore, the conventional organic polymer monoliths do not have a skeletal structure and have a large pore tortuosity factor, and thus inherently have problems such as an increase in back pressure at a high flow rate and morphological change due to their compressibility.
Further, the conventional organic polymer monoliths also have a problem that when directly formed in empty column tubes with an inner diameter of 1 mm or more, they are peeled off from the column tubes due to their own compressibility. This makes it difficult to directly form organic polymer monoliths in empty column tubes.
In order to solve such problems, the present inventors have extensively studied, and as a result have developed a monolith separation medium whose skeletal phase is composed of an addition polymer of a bi- or higher-functional epoxy compound and a bi- or higher-functional amine compound, and has a functional group allowing a new functional group to be introduced thereinto (see Patent Document 1).
Further, another organic polymer monolith is also known, which has a skeletal phase composed of a copolymer of GMA (glycidyl methacrylate) and EDMA (ethylene dimethacrylate) and having amino groups introduced as functional groups by reacting epoxy groups present on the surface thereof with ethylenediamine (see Non-Patent Documents 1 and 2).
Patent Document 1: WO2007/083348 A1
Non-Patent Document 1: Journal of Peptide Science, Vol. 10, pp. 719-730, 2004
Non-Patent Document 2: Journal of Combinational Chemistry, Vol. 4, no. 1, pp. 33-37, 2002